| 1. |
- Younis, Adel, et al.
(författare)
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A perspective on seawater/frp reinforcement in concrete structures
- 2017
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Ingår i: ISEC 2017 - 9th International Structural Engineering and Construction Conference. - : ISEC Press. - 2644-108X. ; , s. 1-6
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Konferensbidrag (refereegranskat)abstract
- Predictions show that more than half of the world population will lack sufficient freshwater by 2025. Yet, the construction industry uses a considerable amount of freshwater to produce concrete. To save resources of fresh water, using seawater seems to be a valid potential alternative that can replace freshwater for mixing concrete. This paper presents a short review performed on existing literature related to the usage of seawater in concrete structures. As a summary of the work presented: (a) It is noticeable that the current literature, generally, reports little or no negative effect of seawater on the characteristics of plain concrete, both in the short and in the long term; (b) steel corrosion caused by the presence of chloride appears to be the sole reason for not accepting the use of seawater in concrete preparation; (c) Fiber reinforced polymer (FRP) is discussed as a promising alternative to steel for seawater-concrete reinforcement, owing to their light weight, high tensile strength, and adequate corrosion resistance; and (d) A future outlook for using seawater accompanied by FRP reinforcement in concrete structures is discussed in terms of achieving sustainability goals.
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| 2. |
- Younis, Adel, et al.
(författare)
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Cost effectiveness of reinforcement alternatives for a concrete water chlorination tank
- 2020
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Ingår i: Journal of Building Engineering. - : Elsevier. - 2352-7102. ; 27, s. 1-12
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Tidskriftsartikel (refereegranskat)abstract
- Reinforced concrete tanks in water/wastewater treatment plants are susceptible to severe corrosion due to aggressive exposure conditions resulting from the application of certain treatment chemicals and methods. Non-corrosive materials, such as stainless steel or fiber reinforced polymer (FRP), may be attractive alternative reinforcement options for such concrete structures. However, the high initial cost of such materials imposes constraints on their use, although such thinking ignores improvements in long-term concrete durability. The current paper addresses the use of non-corrosive reinforcement in a concrete water chlorination tank using life-cycle cost analysis (LCCA) that aims to evaluate the cost effectiveness of different reinforcement alternatives. A comparison was established between four concrete reinforcing materials, namely, black steel, epoxy coated steel, stainless steel, and glass-FRP (GFRP) through a 100-year analysis period. The results of this study suggest that the use of non-corrosive reinforcement helps achieve a considerable long-term cost saving. LCCA showed that GFRP becomes more economical than black steel in 35 years following construction. The net present cost (NPC) obtained for the GFRP-reinforced concrete was approximately 43% lower than that of the black steel reinforced concrete. The use of stainless steel also had a potential advantage but was less cost-effective than GFRP, with a 50-year payback period and an NPC 25% lower than that of the conventional design. Epoxy coated steel also showed a long-term cost benefit when compared to black steel, with approximately 11% reduction in NPC and 15-year extension in the service life. Sensitivity analyses were performed to assess the effects of the analysis period, discount rate, construction costs, concrete strength, and the use of supplementary cementitious materials on the LCCA outcomes.
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| 3. |
- Younis, Adel, et al.
(författare)
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Fresh and hardened properties of seawater-mixed concrete
- 2018
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Ingår i: Construction and Building Materials. - : Elsevier. - 0950-0618 .- 1879-0526. ; 190, s. 276-286
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Tidskriftsartikel (refereegranskat)abstract
- Using seawater for mixing concrete is potentially advantageous from a sustainability perspective. However, the presence of high concentrations of chloride in the seawater can lead to corrosion of steel reinforcement. This issue can be addressed by using non-corrosive reinforcement; e.g., fiber reinforced polymer (FRP) bars. Moreover, the global threat of freshwater scarcity suggests that the use of seawater in concrete mixtures becomes plausible in the future. This paper reports on the results of an extensive experimental study to compare the fresh and hardened properties of freshwater- and seawater-mixed concretes. The experimental program included the following tests: (a) characterization of fresh concrete (slump flow, density, yield, air content, and setting time); (b) mechanical characterization of hardened concrete (compressive strength, splitting tensile strength, and shrinkage); and (c) permeability performance of hardened concrete (rapid chloride permeability, chloride migration, and water absorption). The use of seawater had a notable effect on the fresh concrete properties. Mechanical performance of seawater concrete was slightly lower than that of the freshwater-mixed concrete. The permeability performance of hardened concrete in the two mixtures was similar. Scanning electron microscopy and isothermal calorimetry were used as supplementary tools to better explain the experimental observations. Finally, remedial measures were proposed based on lab trials to improve the properties of seawater concrete.
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| 4. |
- Younis, Adel, et al.
(författare)
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Microstructure investigation of seawater vs. Freshwater cement pastes
- 2019
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Ingår i: ISEC 2019 - 10th International Structural Engineering and Construction: Interdependence between Structural Engineering and Construction Management. - : ISEC Press. - 9780996043762
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Konferensbidrag (refereegranskat)abstract
- Recently, seawater has emerged as viable mixing water for concrete, especially in the case of non-reinforced concrete applications or with the use of non-corrosive reinforcement. Previous studies concerning seawater-mixed concrete mostly revealed an initial slight increase in its strength performance (i.e., till Day 14 following mixing), followed by a strength reduction of 7–15% (i.e., after 28 days or longer) as compared to the conventional freshwater-mixed concrete. With an attempt to explain such observations, this paper aims at comparing the microstructure of freshwater- and seawater-mixed cement pastes. Scanning electron microscopy was utilized to observe the microstructure of freshwater and seawater pastes at Days 3 and 28 following mixing. At Day 3, seawater paste was observed to have more densified microstructure as compared to that of the freshwater counterpart, resulting in relatively higher strength performance. At Day 28, the microstructure was almost similar for the two cement pastes. However, seawater paste was observed to have salt impurities as a result of seawater ions, which possibly cause a slightly lower strength performance as compared to the freshwater paste.
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| 5. |
- Younis, Adel, et al.
(författare)
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Performance of Sewater-Mixed Recycled-Aggregate Concrete
- 2020
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Ingår i: Journal of Materials in Civil Engineering. - : American Society of Civil Engineers (ASCE). - 0899-1561 .- 1943-5533. ; 32:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- The use of seawater and recycled coarse aggregate (RCA) in concrete mixtures leads to the production of a very sustainable concrete. The potential risk of steel reinforcement corrosion (due to chloride in the seawater) in such mixtures may be eliminated when considering plain concrete or noncorrosive reinforcement (e.g., fiber-reinforced polymer). This study investigated the fresh and hardened properties of a proposed green concrete mixed using seawater and recycled coarse aggregates. Two different concrete mixtures were studied, namely conventional concrete (Mix 1) and seawater-mixed concrete with RCA (Mix 2). Blast furnace slag was used as supplementary cementitious material at a 65% replacement level in both concrete mixtures. Fresh and hardened properties of the two concretes, including workability, strength gain, drying shrinkage, permeability, and microstructure, were characterized and compared. The results suggest that the use of seawater and RCA together has negative effects on concrete performance. Compared with the reference (Mix 1), Mix 2 concrete had approximately 5% lower density, 25% lower slump flow, 50% lower setting time, 33% lower strength gain, 10% higher drying shrinkage, 60% higher water absorption, and 100% higher charge passed (in rapid chloride permeability tests). Consequently, strategies to improve the performance of such concretes, such as a reduction in the water:cementitious materials ratio and the use of chemical admixtures, are suggested. These strategies, however, may somewhat reduce the green aspect of the proposed seawater-mixed concrete with RCA.
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| 6. |
- Younis, Adel, et al.
(författare)
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Short-term flexural performance of seawater-mixed recycled-aggregate GFRP-reinforced concrete beams
- 2020
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Ingår i: Composite structures. - : Elsevier. - 0263-8223 .- 1879-1085. ; 236, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Combining seawater, recycled coarse aggregate (RCA), and glass fiber reinforced polymer (GFRP) reinforcement in concrete is potentially advantageous from a sustainability perspective. This paper reports on the results of an experimental study on the short-term flexural performance of seawater-mixed recycled-aggregate concrete beams with GFRP bars. Twelve medium-scale reinforced concrete (RC) beams (150×260×2200 mm) were tested under four-point loading. The test variables included the mixing water (seawater/freshwater), aggregate type (conventional/recycled), and reinforcement material (black steel/GFRP). A wide range of flexural properties, including failure mode, cracking behavior, load-carrying capacity, deformation, energy absorption, and ductility were characterized and compared among the beam specimens. The results suggest that the use of seawater and RCA in concrete has insignificant effects on the flexural capacity of RC beams, especially if concrete strength is preserved by adjusting the mixture design. Altering reinforcement material had a strong influence on the flexural capacity and performance of the tested specimens: the GFRP-RC beams exhibited higher load-carrying capacities (on average 25%) but inferior deformational characteristics as compared to their steel-reinforced counterparts. Theoretical predictions were obtained for the flexural capacity, crack width, and deflection of steel- and GFRP-RC beams based on their corresponding design guides, and compared with the experimental results.
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| 7. |
- Younis, Adel, et al.
(författare)
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Strength, shrinkage, and permeability performance of seawater concrete
- 2019
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Ingår i: ISEC 2019 - 10th International Structural Engineering and Construction: Interdependence between Structural Engineering and Construction Management. - : ISEC Press. - 9780996043762
-
Konferensbidrag (refereegranskat)abstract
- Given the increasing global concern of freshwater scarcity, the use of seawater in concrete mixtures appears to be a way forward towards achieving sustainable concrete, especially in the case of non-reinforced concrete applications or with the use of noncorrosive reinforcement. This paper reports on the results of an experimental study to compare the freshwater- and seawater-mixed concretes in terms of their strength, shrinkage and permeability performance. The experimental program included the following: (i) compressive strength test (at 3, 7, 28, and 56-day ages); (ii) concrete shrinkage test (at Days 4, 7, 14, 21, 28, and 56 following mixing); and (iii) permeability tests (rapid chloride permeability and water absorption at Days 28 and 56 following mixing). As for the study results, seawater concrete showed a slightly higher early-age (i.e., till Day 7) strength performance than that of freshwater-mixed counterpart, followed by a strength performance that is 7–10% inferior to the freshwater concrete after 28 days or later. Also, the shrinkage of seawater concrete was slightly higher than that of freshwater concrete, with a difference of 5% reported after 56 days following mixing. Finally, the permeability performance of hardened concrete in seawater and freshwater mixtures was similar.
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